<html>
    <head>
        <script>
        

let add = () =>{
            var a = document.getElementById('a1').value
            var b = document.getElementById('a2').value
            var c = parseInt(a) + parseInt(b)
            document.getElementById('b').value = c
            
         }
         
        </script>
    </head>
    <body>
           <table>
               <tr>
                   <td>
                  <input type="text" id = "a1"/></td>
               </tr>
               <tr>
                <td>
                    <input type="text" id = "a2"/></td>
            </tr>

            <tr>
                <td><button id="a1" onclick="add()">加</button></td>
                <td><button id="a2" onclick = "sub()">减</button></td> 
                <td><button id="a3" onclick = "multi()">乘</button></td>
                <td><button id="a4" onclick= "divad()">除</button></td> 
            </tr>
            <tr>
                <td>
                    <input type="text" id = "b"/></td>
            </tr>

           </table>
    </body>
    
</html>